1. Field of the Invention
The present invention relates to a connection structure between a plastic gear and an oil pump drive shaft for an internal combustion engine.
2. Background Art
A known method for connecting an oil pump shaft to a gear that transmits a driving force thereto includes the steps of providing a U-shaped groove across a center hole in the gear; fitting a lock pin into a through hole provided perpendicularly relative to a centerline of the shaft; and pushing the shaft into the center hole in the gear, thereby fitting the lock pin into the groove in the gear (see, for example, Japanese Utility Model Publication No. Hei 3-38470, FIGS. 1 and 2).
Since, in this known connecting method, the lock pin is mounted in the through hole of the shaft, provided perpendicularly relative to the centerline of the shaft, an axial position of the shaft is fixed relative to an axial position of the gear. This makes it difficult, due to the lock pin coming off position, to perform phase matching of an oil pump rotor when the gear is not in mesh with a mating gear.
What is needed is an improved connecting structure for connecting a gear to an oil pump drive shaft of an internal combustion engine, which permits easy phase matching relative to a device mounted on the shaft, and easy meshing of a gear, provided on the shaft, with another gear. Preferably, such a connecting structure would non-rotatably fix the position of the gear in relation to the shaft, so that the gear and shaft rotate concurrently together as an integral unit.